Annular combustors for gas turbine engines are typically supported at its aft end to the surrounding diffuser case and serves to inject combustion gases through the high pressure stator vanes to the turbine blades for powering the turbine rotor and generating thrust. Inasmuch as the area of concern of this invention is one of the most hostile environments encountered in the engine, consideration must not only been given to securing the structural integrity of the components, improving maintenance, and assuring that weight and costs are held to a minimum, it must also take into consideration the leakage problems. Since the combustor liner is encased in a surrounding diffuser case that defines with the liner a passageway for directing cooling air from the compressor to cool the combustor and components of the engine located downstream of the combustor, precautions must be made to prevent the leakage so that there will be sufficient air for cooling the other components located downstream therefrom.
This invention constitutes an improvement over U.S. Pat. No. 4,785,623 granted to H. G. Reynolds on Nov. 22, 1988 entitled "Combustor Seal and Support" and assigned to the assignee common to this patent application. This patent, supra, teaches a support that includes complementary lugs on the diffuser case and combustor liner that utilize the radial side surfaces of the lugs to frictionally engage each other to restrict upstream movement. A separate split ring seal is biased against a side edge of the platform of the adjacent high pressure stator vane to seal against leakage from the surrounding cool air passageway into the engine's gas path.
Obviously, since there is radial movement between the complementary surfaces of the lugs, it has been necessary to hard coat these surfaces in an attempt to increase the life of these component parts. Notwithstanding this process which adds significantly to the cost of the parts, these parts, at best, have a limited life span.
Additionally, because of the intimate relationship between the integral lugs on the combustor liner and the complementary integral lugs on the diffuser case it was necessary to hold the tolerances of these parts very closely. These tight tolerances, like the coating, contribute significantly to the cost to manufacture these parts. Another problem that exists in this configuration is the problem evidenced during installation. In assembly the stator vanes are installed after the combustor liners have been installed. Since the split ring and wave spring are loosely held in a U-shaped recess, there is a propensity for them to fall out. Hence, care must be taken when installing the stator vanes that contact is avoided since the insertion of the vanes could easily inadvertently knock out the split ring and wave spring from its operative position.
Other supports for combustors consisted of conical flanges bolted to the diffuser case. Because of the thermal mismatch between the combustor and the diffuser case owing to this environment, these parts evidenced severely high stresses. The large flange of this configuration blocked the flow of cooling air from reaching the high pressure turbine stator vane which necessitated large slots in the conical flange to pass the cooling air to these vanes. This not only adds to the cost of manufacture but also subjects the parts to acquiring fatigue cracks which tend to propagate and limit the part's life.
I have found that I can obviate the problems alluded to in the above by combining the support ring with the seal into a single part. Hence the material selected to fabricate this part doesn't require the hard coat that was necessary to obtain adequate wear resistance parts used in heretofore known designs. In my design the axial movement of the parts relative to each other is inherently restricted which not only simplifies the installation of the combustor but also provides a low stressed axial and radial support as well as damping of vibratory motions encountered.